Temperature control of a workpiece placed on an electrostatic chuck is generally performed using a heater and a chiller unit arranged within the electrostatic chuck. In such a system, cooling is performed by circulating a coolant at a predetermined temperature through a coolant pipe of the chiller unit and heating is performed by applying an alternating current to the heater. Through such heating by the heater and cooling by the chiller unit, the wafer temperature of a wafer placed on the electrostatic chuck may be adjusted to a desired temperature.
In such a system, a low-temperature coolant (fluid) is arranged to be flowing within the chiller unit at a constant flow rate. To raise the temperature in such a state, the heater that is embedded within a stage has to be heated. However, heating takes a relatively long period of time due to the cooling effect of the chiller unit, and such poor responsiveness to temperature control has been a problem.
To address such a problem, a method has been proposed that involves reducing the flow rate of the low-temperature fluid flowing within the chiller unit. However, in such a case, the cooling capacity of the chiller unit is degraded, the cooling speed of the system is decreased, and temperature controllability is degraded. Another potential method involves increasing the capacity of the heater. However, a high frequency power leak current is increased in such a case. That is, in a semiconductor manufacturing device, when a heater is embedded within an electrostatic chuck that is arranged on a stage and is applied a high frequency power, the high frequency power may be leaked outside via a heater line, and the leak current increases as the capacity of the heater is increased.
In applying a high frequency power within a chamber, precautionary measures have to be implemented to prevent the high frequency power from leaking outside the chamber. Accordingly, a heater line and heater power supply filter are arranged to prevent the high frequency power from leaking outside the chamber. However, when the capacity of the heater is increased, the size of the heater power supply filter has to be increased as well. Also, the heater power supply filter has to be arranged close to the member having the heater embedded. Thus, when the size of the heater power supply filter is increased, the heater power supply filter takes up extra space thereby reducing the space for mounting other components.
Accordingly, in another potential method, the temperature may be controlled without using a heater. For example, Patent Document 1 discloses a temperature control system that includes a heating cycle that heats and circulates a fluid, and a cooling cycle that cools and circulates a fluid. The temperature control system is configured to control the temperature of an electrostatic chuck by controlling the flow rate distribution ratios of fluid flowing through circulation paths of the heating cycle and the cooling cycle. In the temperature control system disclosed in Patent Document 1, the heating cycle and the cooling cycle respectively circulate fluids within completely closed and separate pipe systems. A high-temperature fluid indirectly heated through heat exchange with the high-temperature fluid circulating within the heating cycle and a low-temperature fluid indirectly heated through heat exchange with the low-temperature fluid circulating within the cooling cycle are mixed and circulated through a pipe within an electrostatic chuck. The temperature controllability of such a system depends on the amount of fluid that can be stored in heat storage tanks at any given point in time. That is, to maintain the temperature controllability of the above temperature control system, the amount of fluid stored in the heat storage tanks have to exceed a predetermined threshold for ensuring temperature stability.